The present invention relates to an optical disc player signal reading device in which the optical pickup, for instance, a semiconductor laser pickup of an optical video disc player, is movably supported in both the focusing direction and in the tracking or tangential direction.
Heretofore, in order to read information from pits formed on the surface of a video disc in an optical video disc player, it was necessary that the beam spot be controlled so as to be focused on each pit on the video disc as it is rotated and that the beam spot be applied accurately to the pits so that signals can be accurately read from light reflected by the pits. In order to satisfy this requirement, it is necessary to support the pickup in such a manner that the pickup is movable both in the focusing direction or vertically and in the tracking or tangential direction or horizontally.
A conventional pickup supporting technique as shown in FIG. 1 includes a pickup A suspended by a corrugated damper B. This technique is disadvantageous in the following points. Since the damper B is deformable in the focusing direction, when it is required to move the pickup A in the tracking or tangential direction, it is difficult to smoothly move it in the tracking or tangential direction. Furthermore, the fact that the damper is deformable in the focusing direction adversely influences the movement in the focusing direction. In addition, parastic resonance occurring in the damper B itself adversely affects the movement of the pickup A. Because of the position of the drive point with respect to the pickup A and the relation between the drive point and the fulcrum, the pickup cannot smoothly move in the tracking or tangential direction and the pickup A has a tendency to oscillate linearly in the direction of the drive force. The movement of the supporting point of the pickup A is undesirable in that it results in a twisting of the pickup A. Because of these difficulties, the signal reading accuracy utilizing the conventional technique is low. If the size of the pickup is small and it is impossible to mount the pickup at a suitable mounting position because of the positional relationships of the video disc and other devices, the aforementioned abnormal linear oscillation may occur at a frequency within the frequency band of the signals being processed and therefore the pickup may be unusable as a practical matter.
Yet further, a neutral point which is established when the damper B oscillates in the focusing direction or in the tracking or tangential direction may be expected to vary greatly over a period of time. Also, the reliability of the damper as to its strength is regarded as being insufficient.